Experimental and Numerical Study of Swirling ... - Solid Mechanics

Experi imental and Numerical N Stud dy of Swirling g Flow in Scaveenging
Processs
for 2-Stroke
Marin ne Diesel Engin nes
Figu ure 5.16:
Averag ged 3D Velocity
Field at a z 75% port
2
closure e (Color Contour r
represe ent the Normaliz zed
out of f the plane velocit ty
compo onent Vz / V . b
Figu ure 5.17:
Averag ged 3D Velocity
Field at a z 75% port
3
closure e (Color Contour r
represe ent the Normaliz zed
out of f the plane velocit ty
compo onent Vz / V . b
Chapter 5
The in-plane
velocity y profile repreesents
an incrrease
in magnnitude
with thhe
increase e in radial dis stance from thhe
vortex corre
indicating a forced vorteex.
Howeve er, a very dist tinct feature tthat
is observved
is that thee
vortex core is
behavin ng like a sour rce i.e. the fluuid
moves ouutward
from the vortex coore
followin ng a curved path. p This indiicates
that fluid
is undergoing
an outwarrd
movem ment with vorte ex core being the source point.
This patteern
continues to
z wher re due to vor rtex breakdowwn
between ppositions
z aand
z the axiial
2 1 2
velocity y has a wake like profile i. .e. low velocitty
at the vorttex
core (Figuure
5.16). However, H when
flow reachees
position z , this pattern cchanges
and thhe
3
in-plane e velocity distr ribution has nnow
a regular swirling flow pattern (Figuure
5.17). It t must be not ted that throuughout
the floow
from position
z to z , thhe
1 3
tangent tial velocity ha as same profilee
i.e. solid boddy
rotation (Foorced
vortex). A
possible e reason for this
behavior iis
that at highh
Reynolds number
for 755%
port clo osure, the cyli inder inlet proovides
a very small area foor
fluid to entter
into cyl linder resultin ng in a high vvelocity
jet of f the fluid at tthe
intake porrt.
This jet t, from every direction d may meet at some axial distance and then movve
121
Effect of Piston Position